1. Field
The present invention relates generally to wireless communication devices and systems and more specifically to the reduction of power consumption in a dual mode Bluetooth/wireless mobile unit.
2. Background
“Bluetooth” is a wireless personal area network technology supporting wireless voice and data communication between different devices that are typically within ten to one hundred meters of one another. A number of different devices can be Bluetooth-enabled, for example, cell phones, personal digital assistants, and laptop computers. Each such device is equipped with Bluetooth components, including a receiver and transmitter, allowing it to communicate with other nearby, similarly equipped devices, without the use of cables or other physical connections.
As an example, a wireless code division multiple access (CDMA) cell phone can be Bluetooth-enabled, meaning that the cell phone is able to communicate in both the CDMA network and the Bluetooth network. Such a Bluetooth-enabled CDMA cell phone includes both Bluetooth and CDMA components.
In Bluetooth-enabled devices, the Bluetooth component may engage in various “sleep” modes to reduce power consumption. These may also be referred to as “idle” modes. One example is a “page scan” mode, which is utilized when the device is not actively communicating with other Bluetooth-enabled devices, i.e. it is not participating in a Bluetooth network. While in the page scan mode, the Bluetooth component periodically performs a wakeup process during which it scans the surrounding environment to determine whether other Bluetooth-enabled devices are trying to establish communications, in which case the Bluetooth device exits the page scan mode and engages in communications with such devices. If the Bluetooth component encounters another Bluetooth-enabled devices during the wakeup/scanning process and determines that a connection is needed, it can perform certain protocols in order to establish a short-range, wireless connection with that other device. Otherwise, the wakeup/scanning process is turned off until the next wakeup process. The sleep cycle of waking-up, scanning, and turning off repeats typically once, twice, or four times every 1.28 seconds for the duration of the page scan mode. However, certain Bluetooth specifications may vary the timing and pattern of the cycle, for example requiring that the process be performed continuously for 1.28 seconds, or repeating the process sixteen times every 1.28 seconds. Further, certain Bluetooth specifications require that the Bluetooth wakeup process repeat, for example, at least once every 1.28 seconds, every 2.56 seconds, or any other interval required by a particular specification.
In embodiments where the Bluetooth device also includes a CDMA cell phone (“phone”), the phone's CDMA component performs CDMA related tasks while the phone's Bluetooth component scans for other Bluetooth-enabled devices as discussed above. Since CDMA requires precise time synchronization between the phone and the base station, one task of the CDMA component is to synchronize with the base station. In order to synchronize with the base station while in a CDMA idle mode, the CDMA component “wakes up” periodically during its allotted time slots to receive and process pilot signals from the base station on the CDMA paging channel. The CDMA component can synchronize with the base station by processing the pilot signals. For instance, the system time can be determined from the information embedded in the pilot signals.
The wakeup frequency of the CDMA component is governed by the slot cycle index (SCI), which can be set by either the phone or the base station, as is known in the art. If the SCI is zero, the CDMA component performs a wakeup process every 1.28 seconds, i.e. its allotted time slot comes around every 1.28 seconds. As a different example, the SCI can be set at one, in which case the wakeup process is performed every 2.56 seconds, or two, in which case the wakeup process is performed every 5.12 seconds. Thus, lower SCIs mean more frequent wakeup processes, and greater power consumption
At any rate, the dual mode Bluetooth/CDMA device consumes power whether it is the Bluetooth component waking up and scanning for other Bluetooth-enabled devices and then shutting down or the CDMA component waking up and synchronizing with the base station and then shutting down. Further, because each of these independent processes is performed repeatedly, power consumption can be substantial. Since an important advantage of dual mode Bluetooth/CDMA devices is their portability, they often rely on a small battery for their sole source of power. High power consumption in this environment therefore requires more frequent recharging. At best, this is inconvenient. At worst, the dual mode Bluetooth/CDMA device will cease to operate if the battery dies without a nearby recharging source.
Consequently, known dual mode Bluetooth/CDMA devices may not be completely adequate for all users due to their high rate of power consumption.